The central hypothesis of this proposal is that there is an interaction between the sex hormones and the regulation/action of serum leptin. We plan to study the relationship of leptin, sex hormones, and obesity in both male and female pre and post pubertal children. Aims: To measure serum leptin levels and sex hormones in males and females in the pre and post pubertal status. To measure the percent body fat and BMI in these individuals as measures of obesity. To relate serum leptin levels to percent body fat, fasting lipids, blood pressure, insulin resistance and sex.